The present invention relates to a passbook conveyance roller device, in which a passbook-like article is conveyed by a conveyance roller and a pinch roller, which are arranged to be opposed to each other.
A passbook printer provided in, for example, automatic teller machines and passbook handling devices comprises: for example, an entrance and leaving port, through which a user inserts or takes out a passbook; a conveyance roller mechanism provided on a passbook handling path, which extends from the entrance and leaving port; a magnetic stripe read mechanism that reads information of magnetic stripes stuck to a cover of the passbook; an ink jet type printing mechanism, for example, that prints on the passbook on the basis of information read by the magnetic stripe read mechanism; and a page (paper) veerer that turns over a printed page of the passbook. The conveyance roller mechanism comprises a plurality of rows of conveyance rollers and pinch rollers, which are arranged to be opposed to each other, and conveys a passbook to positions of the magnetic stripe read mechanism, the printing mechanism, and the page veerer in response to a command from a control circuit.
By the way, there is disclosed a conveyance roller mechanism provided on a sheet conveyance path of an electrophotographic copier, in which a conveyance roller (drive roller) has a torque limiter function (see, for example, JP-A-6-316346). The conveyance roller comprises a core member made of a resin, fixed on a drive shaft, and formed on an outer peripheral surface thereof with irregularities, and a rubber roller member having a smaller hole than an outside diameter of the core member, the core member being press fitted into the hole of the rubber roller member to be made integral therewith. Thereby, a set torque of the torque limiter function is set by a frictional force generated between the outer peripheral surface of the core member and an inner peripheral surface of the rubber roller member. In the case where, for example, conveyance rollers on an upstream side are set to be smaller in rotational speed than conveyance rollers on a downstream side, the downstream conveyance rollers have the torque limiter function. Thereby, when a conveyed sheet is influenced by the upstream conveyance rollers, the downstream conveyance rollers are put in a state, in which rubber roller members thereof slide relative to core members thereof, to maintain low-speed conveyance, and when a conveyed sheet is not influenced by the upstream conveyance rollers, the downstream conveyance rollers make high-speed conveyance.
The conveyance roller mechanism of the passbook printer is not only required to be heightened in conveyance accuracy, with which printing is made on a passbook, but also must make conveyance in accordance with a change in thickness of printed pages of the passbook. That is, when, for example, the conveyance rollers and the pinch rollers are low in coefficient of friction and pinch force, there is a possibility that slip occurs between a roller and a passbook and a passbook cannot get over a sheet number step caused by a difference between the number of sheets on a cover side of the passbook and the number of sheets on a back cover side thereof and a spine step of a stitched portion. Therefore, it is generally requested to heighten conveyance rollers and pinch rollers in coefficient of friction and pinch force. When conveyance rollers and pinch rollers are heightened in coefficient of friction and pinch force, however, there occurs a possibility that a roller digs a paper surface of a passbook, for example, when jam of the passbook happens to occur. In particular, there is a possibility of damage since a medium, such as a passbook, being thick is hard to buckle.
Hereupon, it is assumed that conveyance rollers having the torque limiter function described above are applied to a conveyance roller mechanism of a passbook printer. Thereby, it is thought that damage to a passbook can be prevented when jam occurs. Since conventional conveyance rollers comprise a rubber roller member, however, there is a possibility that printing ink is transferred (primary transfer to a roller and secondary transfer to a passbook) unlike metallic conveyance rollers when a pinch force is increased with a view to an improvement in conveyance accuracy. Also, with conventional conveyance rollers, irregularities formed on an outer peripheral surface of a core member are formed by satin finish or a multiplicity of axial grooves or the like, and an elastic force of a rubber roller member is generated on a substantially whole circumference of the outer peripheral surface of the core member. Therefore, an elastic force of an elastic member is liable to give rise to distribution and an error, so that it is not possible to exactly set a set torque of the torque limiter function.